Movement disorders are often caused by chronic neurodegenerative diseases such as Parkinson's Disease (“PD”) and Essential Tremor (“ET”). Both of these conditions are currently incurable and cause unintentional muscle movements or human tremors—uncontrollable rhythmic oscillatory movements of the human body. In many cases human tremors can be severe enough to cause a significant degradation in quality of life, interfering with daily activities/tasks such as eating, drinking, or writing.
Patients with movement disorders are typically diagnosed in a clinic using scales such as the Fahn-Tolosa-Marin Tremor Rating Scale for ET or the Unified Parkinson Disease (UPDRS) rating scale for PD. Both of these scales require a trained neurologist to complete and often rely on subjective assessments that occur over a brief period of time in the practitioner's office. Symptom severity at home is typically evaluated from the patient's self-reporting, which is also highly subjective and prone to error.
A particular incapacitating problem associated with chronic neurodegenerative diseases involves freezing, in the upper and/or lower extremities of a patient. Lower extremity freezing and other gait disorders can result in falls and injuries, while upper extremity freezing can hamper day to day activities such as eating and brushing teeth. Thus, upper and/or lower extremity freezing can severely impact quality of life. Furthermore, if a neurologist is attempting to treat a patient for one or more of these conditions, it is often difficult to assess the severity, length, and frequency of freezing events, and whether treatments are helping with such freezing events. Some devices have been used to track lower extremity freezing, but require bulky and obtrusive sensors that a user must wear to track gait. This creates significant challenges when diagnosing, developing and evaluating long-term treatments or interventions for these diseases.